In a large number of analytical reactions, the ability to precisely control reaction parameters is critical. This includes not only controlling basic parameters, such as pH, temperature and the chemical composition of the reactant, but also control over the initiation, termination, and the location of the reaction.
In nucleic acid analyses based on the detection of polymerase-mediated incorporation of nucleotides, control of the initiation of primer extension and the location of the reaction can be very useful, as set forth in copending U.S. Patent Application No. 60/814,433, filed Jun. 16, 2006 and incorporated herein by reference in its entirety for all purposes. Likewise, in many cases, e.g., where one desires to repeatedly perform extension reactions on multiple different primer or template combinations using the same enzyme system, the ability to terminate the interaction between the enzyme and the primer/template complex, thus making way for another primer/template complex, is also of substantial value. The present invention provides these and other benefits.